The invention concerns a telescopic positioning device with an axis, a core component, and a shell component which is shiftable on the core component in an axial direction, with a bolt element provided on the core component for engagement in at least one breach of the shell component, so that, when the bolt element engages in the breach, an axial shifting of core component and shell component is substantially blocked. The bolt element is spring-loaded substantially radially away from the axis in the direction of the bolted position, so that, if the bolt element is placed in radial alignment with the breach, the bolt element necessarily enters into its bolted position, i.e., into the breach. A bolt-releasing surface is provided at the radially outer end of the bolt element, which surface is accessible to the action of external radial forces, e.g., finger action, allowing a radially inward move of the bolt element so that the blocking of the axial shift between the core component and the shell component is released, and so that, after an axial shift has been initiated, a sliding surface of the bolt element enters into sliding engagement with a slideway of the shell component.
Such a telescopic positioning device can be used, e.g., with a pneumatic spring for the opening and positioning of a trunk lid or engine hood of an automotive vehicle. Supporting the opening movement of an engine hood or trunk lid by one or more pneumatic springs has been known for a long time. The pneumatic spring is generally designed such that, perhaps after a manually supported opening operation, it brings the trunk lid or engine hood into the open position by means of the pneumatic spring's push-out force, produced by its compressed-gas content. The spring then maintains the trunk lid or engine hood in this open position. For reclosing the lid or hood, a relatively small force is required, such force supplementing the force-of-gravity moment in overcoming the push-out force of the pneumatic spring. The degree to which an engine hood or trunk lid opens is determined by the stroke of the pneumatic spring. As a rule, there is the option of installing pneumatic springs whose stroke is sufficient to bring the respective body component into an open position that suffices for ordinary operation. However, there also may occur exceptional situations in which a greater degree of opening is desired, e.g., if large bulky objects are to be accommodated in the trunk space of a passenger car or of a hatchback-type vehicle, or if major repairs are to be performed in the engine space of a vehicle. To handle such situations, it is known from German Patent Document P 39 40 916.3 and European Patent Document EP 0 432 767 A1 to slide a shell tube onto the cylinder of the pneumatic spring, the shell tube being axially shiftable with respect to the cylinder. Herein, this shell tube is designated as shell component, and the term core component is used to designate the cylinder of the pneumatic spring. The shell component can have a length about equivalent to the length of the pneumatic-spring cylinder, so that a considerable telescopic path of the shell component with respect to the core component is available. If the opening of one of the automotive-body components is to be set at a degree of opening that exceeds the degree of the opening normally achievable by the moving out of the pneumatic spring, the shell component can be shifted with respect to the core component. In order to attach a pneumatic spring thus modified to the vehicle frame on the one hand, and to the automotive-body component to be pivoted on the other hand, one connecting element is attached, as is customary with pneumatic springs, to the free end of the pneumatic-spring piston, while the other connecting element is attached to the shell component, e.g., to the latter's end that pertains to the bottom of the pneumatic spring.
In order to be able to determine an open position that can be achieved by telescoping the core component out of the shell component, i.e., the pneumatic-spring cylinder out of the shell tube, a bolt element is provided on the core component, which bolt element is capable of engaging into one or several breaches of the shell component. This bolt element is spring-loaded radially outward and necessarily snaps into a breach of the shell component when the open position defined by the position of the breach and of the bolt element has been reached. In this situation, it is customary to attach the bolt element to the end region of the core component (i.e., of the pneumatic-spring cylinder) which is on its bottom side. As a rule, at least two breaches in the shell component are required in order to set the shell component in two positions with respect to the core component, in which case a first position corresponds to the relative position of the shell and core components in which the core component has moved completely into the shell component. The degree of opening of a body component achieved in this relative position of shell and core components corresponds to the opening necessarily produced by the push-out force of the pneumatic spring. However, since one of the connecting elements for linking with the vehicle frame or the movable automotive-body component now no longer is rigidly attached to the core component, but rather to the shell component that is shiftable on the core component, even in the above-mentioned position a bolting of the shell component with respect to the core component is required, since otherwise there would exist the risk, e.g., in the case of a gust of wind on the automotive-body component in its normal open position, that the automotive-body component could be lifted without restriction, the core component being telescoped out of the shell component and, as a result, striking some other portion of the vehicle structure and causing damage therein, or the telescopic guidance between the shell component and the core component being lost and the automotive-body component thereupon dropping back into its closed position, with attendant risk of bodily injury.
A further bolting is required for the shell component's and the core component's length-setting as used in the automotive-body component's open state for special situations.
Accordingly, it is known from the above-referenced German and European patent documents to bolt the shell component with respect to the core component, for one thing in the fully telescoped-in position, and for another to also bolt in a partly telescoped-out position, in which there still remains a sufficient length of guidance between the core component and the shell component.